This invention relates to event data acquisition and, in particular, to systems and methods for logging event data corresponding to processor events in a test device, and maintaining the event data to evaluate the performance of the test device processor.
Software event log tools are used to log microprocessor events on a target system, or test device, for embedded software development and for developing new operating systems. When executing an operating system on a test device, event logging software records processor events such as thread switching, process switching, user directed events, interrupts, mutex and critical section manipulation, memory allocation, and the like to measure processor performance. An event log tool recognizes the processor events and stores associated event data in memory buffers on the test device. Conventionally, the test device temporarily maintains the event data in multiple circular memory buffers, and periodically sends the stored event data to a host computing device that is connected to the test device.
Inherently, a software event log tool affects the performance of a test device processor when measuring the performance of the processor because the event log tool is intrusive. That is to say, a software event log tool affects processor performance by using processor time and one or more processor threads to manage the memory buffers, write the event data to the memory buffers, maintain the event data, and to read and communicate the event data over a transport to a host computing device for performance evaluation.
Another example of software event log intrusion occurs when a user mode processing event is preempted with a system interrupt. A typical solution to prevent a system interrupt when evaluating and/or logging a particular user mode event is to disable the system interrupt. However, this can cause interrupt latencies and unreliable performance characteristics of the test device processor.
Accordingly, there is a need to minimize the intrusion of a test device processor when logging test system events, and a need to generate reliable performance data when logging the events.
An event data acquisition device has a data segment multiplexer to receive data segments corresponding to processor events generated with a test device, and a memory component to maintain the data segments in an order that they are received from the test device. A control component of the event data acquisition device pauses the test device processor when the memory component exceeds a threshold number of stored data segments. The control component also resumes processing of the test device when the memory component maintains less than the threshold number of stored data segments.
In one implementation, the data segment multiplexer timestamps the data segments when they are received from the test device and labels the data segments to identify which have header information and which have event information. The data segments having header information are labeled with a memory address identifier corresponding to a first memory address of the test device, and the data segments having event information are labeled with a memory address identifier corresponding to a second memory address of the test device. An event data packet component generates event data packets where an individual data packet includes data segment(s) having information for a particular processor event.